Earth augers for boring holes in the earth are well known in the art and exemplified by U.S. Pat. No. 4,380,271. This patent describes an auger including a dual flight. Each flight has a leading edge which commences adjacent a pilot bit and a trailing edge which terminates adjacent a chuck. The flights concurrently spiral about a central shaft. A plurality of excavating teeth are arranged in step, radial fashion along the leading edges of the auger flights. During the drilling operations, the cutting teeth cut annular zones of increasing diameter as the auger progresses into the earth.
Typically, the excavating teeth used in connection with the earth auger include a main body portion terminating in a working end and a shank extending upwardly from the main body portion for insertion into the socket of a holder structure on the leading edge of the auger. The main body portion has a leading face which is relieved adjacent the working end to form a recess. One or more flat style inserts are disposed in the recess and are shaped to form a point.
While the excavating teeth described above, have served adequately for many years, one or more of the following problems have been frequently encountered:
(1) The tooth design does not provide adequate protection in high wear areas. Thus, during cutting operations, the body tends to wear excessively due to abrasive action with the rock formation.
(2) The large surface area of the carbide insert wearing against the rock face causes excessive loading which exceeds the rating of the carbide insert. The result is chipping and breaking of the insert rendering the tooth useless for further drilling.
(3) The large surface area and attack angle of the carbide insert creates excessive drag impeding the rate of penetration and reducing drilling performance.
Accordingly, some improvement in the design of excavating teeth is needed.